Charles Watson-Wentworth, second Marquis of Rockingham, is, perhaps, the most overlooked Prime Minister of the eighteenth century. The aim of this thesis is to re-examine the current assessments of the marquis, that he was immature, inept and unfit for high office, and to revise them as necessary. It also aims to indicate the areas where he may have been misjudged. The marquis primarily is placed in his local context of Yorkshire. His upbringing is studied to give same insight into his background and then his roles of landowner and local magnate are examined. His duties of Lord Lieutenant are dealt with by looking at four specific episodes in which he was involved. His political career is investigated at local level both as leader of the Rockingham party and particularly in his ability to influence Yorkshire politics between 1753 and 1782. The udder interests and concerns of Rockingham in Ireland and America are also studied. Rockingham showed great promise as a child although he suffered from a debilitating illness which recurred throughout his life and probably caused his sudden and early death. Far from being incompetent and immature, he was an active estate developer and improver and was a key figure in the social, economic and political life of the neighbourhood of Wentworth Woodhouse. He virtually controlled Yorkshire politics for twenty years and led the largest and best-organized opposition party in parliament during that time. His views on the problems of Ireland and America have been under-valued and his personal qualities both for attracting loyalty and friendship and for his active leadership of his party have not been given sufficient recognition. In spite of his faults Rockingham was far more capable and a far more complex person than has been realised.